Method and apparatus for expelling moisture from tobacco



June 25, 1968 w. WOCHNOWSKI 3,389,707

METHOD AND APPARATUS FOR EXPELLING MOISTURE FROM TOBACCO Filed July 15,1966 INVENTOR. (/4 #dauzNl/MML BY I MMJ- Min r United States Patent3,389,707 METHOD AND APPARATUS FOR EXPELLING MQISTURE FROM TOBACCOWaldemar Wochnowski, Hamburg, Germany, assignor to Hauni-Werke Koerber &(10., KG, Hamburg-Bergedorf, Germany Filed July 15, 1966, Ser. No.565,426 Claims priority, application Great Britain, July 22, 1%5,31,264/ 65 31 Claims. (Cl. 131-135) The present invention relates to amethod and apparatus for conditioning tobacco by expulsion of surplusmoisture. More particularly, the invention relates to improvements in amethod and apparatus for controlled expulsion of moisture from acontinuous stream of tobacco particles.

It is already known to expel moisture from a tobacco stream by conveyingsuch stream through a series of separate driers in each of which thestream is heated to expel therefrom moisture in a series of successivestages. A serious drawback of such methods and apparatus is that theoperation is too expensive and that the expulsion of moisture requirestoo much heat energy. This is due, at least to a certain extent, to thefact that, while travelling between successive driers, the particles ofthe tobacco stream are exposed to atmospheric air.

Accordingly, it is an important object of the present invention toprovide a method of expelling moisture from a continuous stream oftobacco particles in such a way that the operation consumes little heatenergy.

Another object of the invention is to provide a highly versatile andcompact apparatus which may be utilized in carrying out the improvedmethod.

A further object of the invention is to provide an apparatus of the justoutlined characteristics which can be readily converted for treatment oftobacco particles containing relatively small or relatively highpercentages of moisture.

An additional object of the invention is to provide a novel heatingsystem which can be utilized in the above outlined apparatus.

A concomitant object of the invention is to provide an apparatus forexpelling moisture from tobacco which, though provided with a singledrier, is capable of treating each successive increment of the stream ina plurality of stages and in such a way that the amount of heat energyconsumed in each such stage is selected as a function of certainimportant characteristics of tobacco particles.

Briefly stated, one feature of my invention resides in the rpovision ofa condition ng apparatus which may be utilized for expelling moisturefrom freshly destalked tobacco leaf laminae or from cured lea-f laminaesubsequent to shredding. In its simplest form, the apparatus comprises afeed arranged to advance a stream of moist tobacco lengthwise toward,through and beyond a conditioning zone, a drier preferably assuming theform of a rotary drum which is accommodated in the conditioning zone anddefines a continuous conditioning chamber having an intake end whichreceives successive increments of the stream and a discharge end fromwhich such increments issue, heating means comprising a pair of supplymeans the first of which admits into the intake end of the conditioningchamber at least one first current of hot air or other suitable fluidwhich flows concurrent with the stream and expels moisture from tobaccoand the second of which admits at least one second current of hot fluidinto the discharge end of the conditioning chamber whereby such secondcurrent or currents flow countercurrent to the stream and expeladditional moistrue from tobacco, and evacuating means communicating3,339,7b7 Patented June 25, 1968 with the conditioning chamberintermediate the intake and discharge ends of this chamber to receivethe first and second currents from the drier.

The heating means preferably comprises two adjustable heating units eachof which includes one of the aforementioned supply means and each ofwhich can be adjusted by a separate control unit. One of these controlunits is arranged to adjust the respective heating unit in accordancewith changes in one or more characteristics of the stream which entersthe intake end of the conditioning chamber and the other control unitadjusts the corresponding heating unit in accordance with changes in oneor more characteristics of the stream after such stream leaves theconditioning chamber. For example, each of the control units maycomprise a weighing device and/ or a moisture detector.

The novel features which are considered as characteristic of theinvention are set forth in particular in the appended claims. Theimproved tobacco conditioning apparatus itself, however, both as to itsconstruction and its mode of operation, together with additionalfeatures and advantages thereof, will be best understood upon perusal ofthe following detailed description of certain specific embodiments withreference to the accompanying drawings, in which:

FIG. 1 is a diagrammatic side elevational view of a tobacco conditioningapparatus which embodies one form of my invention, a portion of thedrier being broken away;

FIG. 2 is a transverse vertical section through the drier and evacuatingmeans substantially as seen in the direction of arrows from the lineIIII of FIG. 1; and

FIG. 3 is a fragmentary axial section through the drier and evacuatingmeans.

Referring first to FIG. 1, there is shown a conditioning apparatus whichcomprises a feed 10, 12, 16, 8, 18, 2G, a drier 2, heating meansincluding two adjustable heating units 28, 48 and a third or auxiliaryheating unit 148, two control units 135, 136 and an evacuating device 76serving as a means for selecting the areas in which the heating units28, 48 are effective. The feed is arranged to advance a stream T oftobacco leaves lengthwise and through the conditioning chamber 2a (seeFIG. 2) of the drier 2. This drier resembles a hollow cylinder or drumwhose axis is inclined downwardly, as seen in the direction of feed, sothat successive increments of the stream T which are admitted at theintake end of the conditioning chamber 2:: tend to advance automaticallythrough and to leave the conditioning chamber in response to rotation ofthe drier. Therefore, the variable speed motor 8 which rotates the drier2 can be said to form part of the feed for the tobacco stream T. Thedrier is rotatable on supporting rolls 1 which are mounted in bearingbrackets 4 and 6, and the output shaft of the motor 8 carries a pinion 3which meshes with a ring gear 5 at the intake end of the conditioningchamber 2a. Instead of utilizing a variable speed motor 8, the feed ofmy conditioning apparatus may comprise a constant-speed motor and avariable speed transmission whose output shaft is then connected withthe pinion 3 in a manner as disclosed, for example, in US. Patent No.3,039,201 to Esenwein.

In addition to the motor 8, the feed includes a conveyor belt 10 whichadvances the stream T lengthwise in the direction indicated by an arrow7 so that successive increments of the stream descend onto a secondconveyor belt 12 which cooperates with a first detector 12a forming partof the control unit 135. The detector 21a constitutes a weighing devicewhich weighs successive increments of tobacco in the stream T andproduces impulses which are indicative of the measured results. Theconveyor belt 12 delivers the tobacco stream T into a vibrating trough14 forming part of a dielectric moisture detector of the type disclosed,for example, in the copending application Ser. No. 192,834 to Esenweinwhich is assigned to the same assignee. The dielectric moisture detectordetermines the moisture content of successive increments of tobacco inthe stream T (in percent) and produces impulses which are indicative ofthe results of such measurements. This detector also forms part of thecontrol unit 135.

The trough 14 discharges tobacco into an inclined chute 16 whichdelivers such tobacco into the intake end of the conditioning chamber 2ain the rotary drier 2. Successive increments of conditioned tobacco aredischarged into a second inclined chute 18 which delivers such tobaccoonto a conveyor belt 20, and this belt in turn discharges tobacco into avibrating trough 22 forming part of a second dielectric moisturedetector and constituting a component of the second control unit 136.

The auxiliary heating unit 148 comprises a series of heating elementshere shown as coils 24 which extend along the full length of theconditioning chamber 2a and are supported by the drier 2 so that eachsuch coil rotates about the axis of the drier when the motor 8 is on. Asshown in FIG. 2, the coils 24 are distributed in such a way that theyform vanes or blades which perform an agitating and mixing action tomake sure that the particles of the stream T are loosened and intermixedand that each such particle is fully exposed to undergo a highlysatisfactory drying or moisture expelling treatment. The coils 24 of theheating unit 148 are connected to a header 24a which is accommodated inthe discharge end of the conditioning chamber 2a and rotates with thedrier 2. This header 24:: receives hot water, steam or another suitableheating fluid from a supply pipe 26. A discharge pipe 27 serves toevacuate spent heating fluid from the coils 24. The coils 24 heat thetubular wall 62 of the drier 2 so that the particles of the stream T areheated by contact with the coils 24 as Well as by contact with theinternal surface of the wall 62. The coils 24 of the auxiliary heatingunit 148 can be replaced by electrically heated heating elements and thewall 62 of the drier 2 can be heated independently of such heatingelements without in any way departing from the spirit of my invention.The wall 62 resembles a hollow cylinder.

The first adjustable heating unit 28 operates with hot air and comprisesa blower 34 whose pressure side is connected with a supply pipe 36discharging into the intake end of the conditioning chamber 2a. Theinlet of the blower 34 is connected with a suction pipe 32 whose intakeend accommodates an electric resistance heater 30 so that the current ofair drawn into the pipe 32 is heated prior to flowing past an adjustablevalve 38 constituting the adjusting means of the control unit 135. Thisvalve 38 controls the admission of relatively cool atmospheric airthrough a nipple 37 which is connected with the suction pipe 32. Thus,the momentary position of the valve 38 will determine the temperature ofthe current of hot air which flows into the supply pipe 36 and thenceinto the intake end of the conditioning chamber 2a. The position of thevalve 38 can be adjusted by a servomotor 40 which forms part of thecontrol unit 135. The current of hot air issuing from the supply pipe 36flows concurrent with the tobacco stream T and traverses successiveincerements of the stream even before such increments descend intoactual contact with the coils 24 and/or with the wall 62. This aircurrent also performs a combined agitating, loosening and mixing actionand this contributes to more uniform drying of the stream T.

The second adjustable heating unit 48 also operates with hot air andcomprises a blower 134, a supply pipe 56 which discharges into thedischarge end of the conditioning chamber 2a a suction pipe 132 whoseintake end accommodates an electric resistance heater 130, a valve 50which is installed in the suction pipe 132 and constitues the adjustingmeans of the second control unit 136, and a nipple 51 which can admitrelatively cool atmospheric air into the suction pipe 132 at the ratedetermined by the position of the valve 50. This valve is adjustable bya servoinotor 52 of the control unit 136. It will be noted that thecurrent of air issuing from the supply pipe 56 flows countercurrent tothe tobacco stream T, i.e., in a direction toward the intake end of theconditioning chamber 2a and counter to the direction of flow of thecurrent which issues from the supply pipe 36 of the first adjustableheating unit 28.

A substantially centrally located median portion 83 of the wall 62 ofthe drier 2 is formed with apertures or perforations 34 which areclosely adjacent to each other. Thus, the perforated median portion 83forms a foraminous annulus or sieve intermediate the axial ends of thewall 62. The dimensions of the apertures 84 are selected in such a waythat they permit escape of fluid but that the particles of tobaccoforming the stream T remain in the conditioning chamber 20.

The sieve 83 is surrounded by an annular fluid collector or hood 64which forms part of the evacuating device 76 and is movable axially ofthe wall 62 as indicated by a double-headed arrow 76a. This hood 64comprises two annular end portions or flanges 65, 67 which are inscaling engagement with the external surface of the wall 62 and aredisposed substantially at the opposite axial ends of the sieve 83. Thehood 64 defines with the wall 62 an annular compartment 113 whichcommunicates with the central region of the conditioning chamber 2athrough the perforations 84. As shown in FIG. 3, the axial length of thecompartment 113 is somewhat less than the axial length of the sieve 83.The difference between the two axial lengths can approximate thethickness of the flange 65 or 67.

The numeral 68 denotes a pipe also forming part of the evacuating device76 and serving to receive or to withdraw fluid from the compartment 113.This evacuating device 76 further comprises a substantially conical orfunnel-shaped portion 66 which is connected with the hood 64 and pipe 68in such a way that its cross-sectional area diminishes in a directionaway from the compartment 113. The discharge end of the pipe 68 isconnected to a fan 68a or another suitable suction generating devicethrough the intermediary of a flexible hose 112.

The hood 6-4 is reciprocable axially of the drier 2 (arrow 76a) to theextent determined by two annular external stops or collars 80, 82provided on the wall 62. The lefthand end position of the hood 64 isshown in FIG. 1 by solid lines. the phantom lines indicate theright-hand end position of the hood 64 when the latters flange 67 abutsagainst the collar 80. When the hood 64 assumes the solid-line positionof FIG. 1, its flange 67 overlies and seals a group of perforations 84at the righthand axial end of the sieve 83. In other words, thecompartment 113 then communicates with the conditioning chamber 2a onlythrough such perforations 84 which are located at a relatively greatdistance from the supply pipe 56 of the second adjustable heating unit48 so that the current of hot air issuing from the pipe 56 will cover agreater distance prior to being drawn into the compartment 113 andthence into the pipe 68. If the hood 64 is thereupon shifted to itsphantom-line position, the distance which the current of hot air issuingfrom the supply pipe 56 must cover on its way into the compartment 113is reduced. The reverse holds true for the current of hot air whichissues from the supply pipe 36 of the first adjustable heating unit 28.In the phantom-line position of the hood 64, the left-hand flange 65seals a group of perforations 84 at the left-hand axial end of the sieve-83. Of course, the hood 64 can be moved to any desired number ofintermediate positions each of which corresponds to a different distancewhich the currents of hot air issuing from the supply pipes 36, 56 mustcover on their Way into the compartment 113. The combined crosssectionalarea of all such perforations 84 which remain exposed in any desiredaxial position of the hood 64 is always the same and the perforationswhich are surrounded by the flange 65 and/or 67 are airtightly sealedfrom the compartment i113.

The means for shifting the hood 64 axially of the drier 2 comprises athreaded spindle 70 One end of which is rotatably afiixed to the funnel66 and which meshes with a fixed spindle nut 72. The other end of thespindle 70 carries a hand wheel 74 or an analogous actuating devicewhich can be rotated by hand or by remote control to select the exactaxial position of the hood 64. If desired, the spindle 70 may beprovided with an index which is movable with reference to a fixed scalewhose graduations indicate various axial positions of the hood 64.

The pipe 68 withdraws or receives the air currents which are admitted bythe supply pipes 36 and 56 as well as all such vapors which develop inresponse to drying of tobacco in the conditioning chamber 2a. Ifdesired, the pipe 68 can be arranged to discharge such air currents andvapors directly into the atmosphere, i.e., the fan 68a can be dispensedwith.

It will be seen that the currents of air admitted by the supply pipes36, 56 respectively flow concurrent and countercurrent with reference tothe direction of tobacco feed and are withdrawn from the conditioningchamber 2a via perforations 84, compartment 113, and pipe 68. The twoair currents meet in a region somewhere between the axial ends of thedried 2 (depending on the momentary axial position of the hood 64). Thehood 6-4 cannot rotate with the dried 2 because the funnel 66 isconnected with the spindle 70. In other words, save for relatively smallaxial movement in response to rotation of the spindle 79, the entireevacuating device 76 remains stationary. If this evacuating device isprovided with a fan, such as the fan 68a, it also comprises the flexiblehose 112 (shown in FIG. 2) so that the fan 6811 need not move with thehood 64. Alternatively, the entire pipe 68 may consist of flexiblematerial.

It was found that the heating action of air currents which aredischarged by the supply conduits 36, 56 is more intensive in thatregion of the conditioning chamber 2a which is located diametricallyopposite the funnel 6 6 of the evacuating device 76. Such localizedintensification of heating atcion is particularly strong when the fan 68is on. In order to eliminate -(or at least to reduce) localizedintensification of heating action, the evacuating device 76 may comprisea series of pipes 68 and an equal number of hoses 112 which aredistributed circumferentially of the hood 64 and are connected to acommon suction fan or to a series of separate fans. A second flexiblehose 112' is indicated in FIG. 2 by phantom lines.

The control unit 135 comprises the aforementioned dielectric detectors12a, 14, the valve 38 and the servomotor 40. This control unit 135 ispreferably identical with or analogous to that described and claimed inthe copending application Ser. No. 411,788 of Koch et al. which isassigned to the same assignee. Therefore, the exact construction of thecontrol unit 135 (and/or 136) forms no part of the present invention.

The detector or weighing device 12a. of the control unit 135 sendsimpulses to a transducer '85 which converts such impulses intoappropriate electrical signals and transmits the signals to a junction88. The junction 88 is further connected with the output of a secondtransducer 86 which receives impulses from the dielectric moisturedetector including the trough 14. A third transducer 46 transmits to thejunction 88 signals which are generated in response to impulsestransmitted by a third detector 44 located in the supply pipe 36 andserving to measure the temperature of the air current which is admittedinto the intake end of the conditioning chamber 2a.

The control unit 135 also comprises a suitable rated value selectingdevice 108 whose output is connected with the junction 88 and which canbe adjusted manually by means of a handle 109 or the like. The junction88 will transmit signals through two amplifiers 90, 92 and on to theservomotor 40 for the valve 38 when the signal emitted by the device 108is not cancelled by signals transmitted to the junction 88 from theoutputs of the transducers 46, 85 and 86.

The second control unit 136 includes the aforementioned valve 56, itsservomotor 52, the dielectric moisture detector which includes thetrough 22, and a junction 96 which receives signals from the output of atransducer 94 connected to the dielectric detector. The junction 96 isfurther connected with the output of a rated value selecting devicewhich is adjustable by a handle 111. The connection between the junction96 and the servomotor 52 for the valve 50 comprises three amplifiers100, 102 and 104. The amplifier 164 has two Outputs one of which isconnected to the servomotor 52 and the other of which is connected withthe input of a timer 106. This timer can send signals to the junction 96through a conductor 116. The control unit 136 also comprises a seconddetector 58 which is installed in the supply pipe 56 to measure thetemperature of the hot air current flowing toward the discharge end ofthe conditioning chamber 2a. The detector 58 is connected with the inputof the amplifier 102 through a transducer 60.

The operation of my conditioning apparatus is as follows:

The tobacco stream T can consist of shredded tobacco or of tobacco leaflaminae coming directly from a separator which receives a mixture ofleaf laminae and ribs or veins from a stripping or destalking machine.In other words, the particles of the stream T can consist of cured oruncured tobacco. The operation of the distributor or another suitableunit which feeds tobacco to the conveyor belt 10 is preferably asuniform as possible so that each succesive increment of the stream Tpreferably contains the same or approximately the same amount oftobacco. The moisture content of the particles in the stream T is to bereduced in the conditioning chamber 2a under the action of the threeheating units 28, 48 and 148.

The detector 12:: weighs successive increments of the stream T andproduces impulses which are indicative of such measurements. Theimpulses are transmitted to the transducer 85 which transmitsappropriate signals to the junction 88 of the control unit for the firstadjustable heating unit 28. During travel through the vibrating trough14, the dielectric moisture detector of the control unit 135 determinesthe moisture content of each successive increment and produces impulseswhich are transmitted to the transducer 86. The latter transmit electricsignals to the junction 88. The drier 2 is rotated by the motor 8 sothat the particles admitted by the inclined chute 16 are entrained bythe vanes formed by the coils 24 of the auxiliary heating unit 148 andare repeatedly lifted from a lower level to a higher level whence theparticles descend back to the lower level to be separated from eachother and to be fully exposed to the heating action of coils 24, of theheating wall 62 and of the air current admitted by the supply pipe 36 ofthe first adjustable heating unit 28. Since the axis of the drier 2 isinclined downwardly toward the chute 18, the orbiting coils 24 causesuccessively admitted increments of the stream T to travel through,toward and beyond the discharge end of the conditioning chamber 2a. Theincrements of the tobacco stream T are heated by the current of airadmitted by the supply pipe 56 and pass through the chute 18, along theupper stringer of the belt 20 and into the vibrating trough 22 of thedielectric moisture detector in the second control unit 136. Thisdetector sends impulses to the transducer 94 which transmits electricsignals to the junction 96 of the control unit 136. The trough 22discharges the particles of the stream T onto a further conveyor (notshown) which serves to adavnce the stream to a further processingstation.

The purpose of the auxiliary heating unit 148 is to subject the tobaccostream T to a constant heating action, i.e., to supply a certain minimumamount of heat energy which is invariably required for properconditioning of tobacco. The heating action of the unit 148 can beselected by adjustment of a steam valve 26a in the supply pipe 26, andsuch heating action then remains unchanged. The header 24a seals oralmost seals the discharge end of the conditioning chamber 2a so thatthis discharge end receives air only or mainly from the supply pipe 56.The intake end of the chamber 2a is also closed against entry ofatmospheric air so that this intake end receives tobacco from the chute16 and a current of hot air from the supply pipe 36. The air currentissuing from the supply pipe 36 passes through successive increments ofthe stream T before such increments descend onto the orbiting coils 24and/or onto the internal surface of the revolving wall 62 in the lowerzone of the conditioning chamber 2a so that the particles are subjectedto a further heating, loosening and agitating action. The heating actionof the unit 28 is felt mainly in the upstream section of theconditioning chamber 2a which extends between the left-hand axial end ofthe drier 2 and the unsealed perforations 84 of the sieve 83. Since thecoils 24 of the auxiliary heating unit 148 repeatedly lift the particlesof the stream T from a lower level to a higher level and allow the thuslifted particles to descend back to the lower level, each individualparticle is allowed to come into intimate contact with the current ofhot air issuing from the supply pipe 36 of the first adjustable heatingunit 28. The temperature of the air current issuing from the supply pipe36 depends on the position of the valve 38 in the suction pipe 32, andthe position of this valve depends on the magnitude of signalstransmitted to the servomotor 40. If the valve 38 admits more air fromthe nipple 37, the temperature of the air current which enters thesupply pipe 36 is reduced. The magnitude of signals which aretransmitted to the servomotor 4t) depends on the measurements carriedout by the two upstream detectors (weighing device 12a and thedielectric moisture detector which includes the trough 14). The signalstransmitted to the junction 88 of the control unit 135 for the firstadjustable heating unit 28 are compared with signals emitted by therated value selecting device 108 and the resulting positive 01' negativesignal is transmitted to the servomotor 40 via amplifiers 90, 92 tobring about appropriate adjustments in the position of the valve 38. Inother words, if the dielectric moisture detector of the control unit 135detects that the moisture content of successive increment of the streamT is higher than warranted by the setting of the device 108, theservomotor 40 will cause the valve 38 to reduce the inflow of cold airthrough the nipple 37 so that the temperature of the air currententering the supply pipe 36 rises. Also, and if the moisture content ofthe stream T upstream of the drier 2 is satisfactory but the weighingdevice 12a detects an increase in the rate at which the stream T flowstoward the drier, the servomotor 40 will adjust the valve 38 in such away that the latter reduces the inflow of cold air via nipple 37, i.e.,the heating action of the unit 28 is intensified because theconditioning chamber 2a receives more tobacco per unit of time.

The detector 44 in the supply pipe 36 senses all variations in thetemperature of the air current which enters the intake end of theconditioning chamber 2a and transmits impuses to the transducer 46 whichtransmits appropriate signals to the junction 88. This purpose of thedetector 44 is fully disclosed in the aforementioned copendingaplication Ser. No. 411,788 of Koch et al. An important function of thisdetector is to prevent sudden and substantial changes in the temperatureof air which is discharged by the supply pipe 36.

When the successive increments of the stream '1 leave the upstreamsection of the conditioning chamber 2a, they are subjected to theheating action of the air current which is discharged by the supply pipe56 of the second adjustable heating unit 48. This air current flowscounter to the direction of travel of the tobacco stream T. The heatingaction of the unit 48 is regulated by the control unit 136 as a functionof the moisture content of successive increments which have left thedrier 2 and pass through the trough 22 of the second dielectric moisturedetector. Signals transmitted by the transducer 94 in response toimpulses received from this moisture detector are utilized to operatethe servomotor 52 which adjusts the valve 50 in a sense to admit morecool air via nipple 51 if the moisture content of increments travellingin the trough 22 is below a value selected by the device 110. If themoisture content is too high, the valve 58 reduces the inflow of coldair via nipple 51 so that a greater percentage of the air currentissuing from the supply pipe 56 is heated by the heater in the suctionpipe 132.

The detector 58 and the associated transducer 60 of the control unit 136constitute a damper which performs an equalizing or smoothing action toprevent sudden variations in the temperature of the air current enteringthe discharge end of the conditioning chamber 2a.

The operation of the second adjustable heating unit 48 and therespective control unit 136 is based on the premise that any changes inthe moisture content of successive increments of the tobacco stream Tissuing from the conditioning chamber 2a are gradual, i.e., that anincrement having a relatively high moisture content does not followimmediately an increment whose moisture content is much lower, or viceversa. Also, it takes a certain amount of time before a change in theheating action of the unit 48 is sensed by the dielectric moisturedetector which includes the trough 22. The purpose of the timer 106 isto compensate for eventual fluctuations in the regulatin action whichare due to such time lag between changes in heating action of the unit48 and detection of the effect of such changes upon the moisture contentof increments which travel in the trough 22. As stated before, the timer106 is connected with one of two outputs of the amplifier 104 and sendsdelayed signals whose magnitude is inversely proportional to themagnitude of output signais received from the amplifier 194. This delaysthe operation of the servomotor 52 by an interval which corresponds tothe time constant of the timer 106. Such time constant is selected independency on that interval of time which elapses between a change inthe temperature of hot air issuing from the supply pipe 56 and thedetection of the effect of such change in response to measurement ofmoisture content in the trough 22.

The resistance which the blowers 34, 134 of the adjustable heating units28, 48 encounter in drawing air through the suction pipes 32, 132depends on the momentary setting of the valves 38, 50. If these valvesadmit relatively large quantities of cool air (nipples 37 and 51), theresistance which the blowers 32, 132 must overcome is reduced, and viceversa. The output of these blowers depends from the resistance whichthey must overcome in forcing air into the supply pipes 36, 56, Le, thethroughput of the heating units 28, 48 is higher if the temperature ofthe respective air currents is lower. For example, and if the valve 33of the control unit 135 is adjusted in a sense to reduce the inflow ofcold air via nipple 37, and if the valve 5% of the control unit 136 isadjusted in the opposite sense so that the temperature of the aircurrent issuing from the supply pipe 56 is lower, the rate of airadmission into the upstream section of the conditioning chamber 20 islower than in the downstream section. This means that the region wherethe two air currents meet is shifted toward the intake end of thechamber 2a and the effect of hot air admitted by the pipe 56 is feltalong a greater part of the conditioning zone which accommodates thedrier 2.

The purpose of the aforementioned evacuating device 76 which includesthe axially movable hood 64 is to withdraw or receive the air currentsadmitted by the supply pipes 36, 56 exactly in the region where the twoair currents meet. All that is necessary is to rotate the spindle 70through the intermediary of the hand wheel "/4 so that the hood 64 movestoward or away from the collar 82. The solid lines show in FIG. 1 thehood 64 in its left-hand end position. When the hood 64 is caused tomove to such position, the air current issuing from the supply pipe 56is effectve along a greater part of the conditioning chamber because theair current admitted by the supply pipe 36 is assumed to be relativelycool. It goes without saying that the operators can influence the exactposition of the region where the two air currents meet by changing theaxial position of the hood 64 independently of the exact setting of thevalve 38 and/or 50. As a rule, the region where the two air currentsmeet will be shifted in the same direction in which the hood 64 isshifted by the spindle 70. This is invariably true if the setting of thevalves 38 and 59 remains unchanged. Such axial adjustability of the hood64 enables the operators to intensify the preliminary heating action(unit 28) at the expense of the secondary or final heating action (unit48) or vice versa.

It will be seen that the control units 135, 136 regulate the heatingaction of the heating units 28 and 48, i.e., that the heating action ofthe third or auxiliary heating unit 148 is not dependent on measurementsof one or more characteristics of hte tobacco stream T upstream and/ ordownstream of the conditioning zone. As stated before, the heatingaction of this auxiliary unit is selected in advance and thereuponpreferably remains constant so that any changes in the moisture contentand/or in the rate of admission of the tobacco stream T are compensatedfor by regulation of the heating action of the unit 28 and/or 48. Theauxiliary heating unit 148 supplies a predetermined minimum amount ofheat energy which is invariably necessary and which enables theadjustable heating units 28, 48 to operate with lesser quantities of hotair so that they can react more rapidly to changes in the moisturecontent and/or to changes in the weight of successive increments of thestream T. Stated otherwise, the auxiliary unit 148 supplies such heatenergy which would have to be furnished by the heating units 28, 48regardless of changes in the weight and/or the moisture content of thestream T. The provision of this auxiliary heating unit 148 constitutesan advantageous feature of our conditioning apparatus because itsheating action need not be too intensive so that the particles of thestream T which come in direct contact with the heated coils 24 and wall62 are not subjected to excessive heating action. In other words, theheating action of the auxiliary unit 14-8 is invariably selected in sucha way that tobacco particles passing through the chamber 2a are notsubjected to excessive heating by direct contact with steam-heated partsof the apparatus.

In conceiving my present invention, I was guided by the followingconsiderations: It a tobacco stream which passes through theconditioning chamber of a drier is heated only by a current of hot fluidwhich flows concurrent with the stream, i.e., from the intake end towardand through the discharge end of the conditioning chamber, the drop intemperature of the air current is not linear because the progressing aircurrent comes in contact with increments whose temperature increases inthe direction of air flow. In other words, the main conditioning actionof such an air current is concentrated at the intake end of theconditioning chamber.

If the tobacco stream passing through the conditioning chamber is heatedsolely by a current of hot air which fiows from the discharge end towardand through the intake end of the drier, the drop in temperature of airis almost linear but the air current is effective solely or mainly inthe downstream section of the conditioning chamber.

If the current of hot air were admitted into the median region of theconditioning chamber and were caused to flow upstream toward the intakeend as well as downiii stream toward the discharge end of the chamber,the conditioning action of such air would be concentrated mainly in themedian region. By admitting the air in the just outlined way, thetobacco particles advancing through the upstream portion of the drierwould flow countercurrent to the flow of air and the particles advancingthrough the downstream part of the drier would advance concurrent withthe flow of air. Also, the air would be admitted in a region which islocated at a maximum distance from the detectors which measure themoisture content upstream and downstream of the conditioning chamber.Due to such maximum distance between the zone of air admission and thedetectors, the detectors would be too late in detecting eventualvariations in moisture content (and/or other characteristics of thestream) and it could happen that long portions of the stream would betreated improperly.

In accordance with an important feature of my invention, the twocurrents of air are controlled independently of each other, i.e., bycontrol units 135, 136 whose detectors are respectively located upstreamand downstream of the conditioning chamber 2a. Since the upstreamdetector 1211, 14 control the temperature of air which is admitted atthe upstream end of the conditioning chamber 2a, they are located at aminimum distance from the first adjustable heating unit 28. The sameholds true for the detector 22 or detectors which determine thecharacteristics of the tobacco stream T downstream of the conditioningchamber 2a and control the second adjustable heating unit 48.

It was further found that the major percentage of surplus moistureshould be withdrawn in the upstream section of the conditioning chamber2a, i.e., by heat energy transmitted to tobacco by the left-handportions of the coils 24, by the left-hand portion of the wall 62, andby the air current issuing from the supply pipe 36 of the firstadjustable heating unit 28. In most instances, the effect of the heatingunit 28 will be felt exclusively in the upstream section of the chamber2a. The second adjustable heating unit 4-8 carries of a correctiveheating action which is not as intensive as the heating action in theupstream part of the drier 2 but is sufiiciently effective to insurethat the stream T leaving the chamber 2a will have a desired moisturecontent, i.e., that the moisture content of each successive increment ofthe stream will remain Within a relatively narrow range. The detector12a constitutes an advantageous optional feature of the control unit135, and its provision is particularly desirable when the tobacco streamT is not formed at a constant rate so that each successive unit lengthof this stream does not contain the same amount of tobacco particles.

The exact percentage of moisture which should remain in tobacco thatleaves the conditioning chamber 2a depends on many factors. For example,such percentage will depend on the type of tobacco, on the dimensions oftobacco particles, and on the desired characteristics of the ultimateproduct. Such percentage can be selected by appropriate adjustments ofthe rated value selecting device 108 and/or 1G9.

It is clear that the control unit and/or 136 could also operate withdetectors which measure the characteristics of the tobacco stream T atshorter or longer regular or even irregular intervals. However, it wasfound that the conditioning operation is much more reliable if thedetectors are arranged to scan each successive increment of the tobaccostream.

Adjustments of the evacuating device 75 in the axial direction of thedrier 2 are desirable for the reasons which were discussed hereinaboveand also in view of the following considerations. If the tobacco streamT contains a relatively high percentage of moisture and should berelieved of a substantial amount of surplus moisture, the current of hotair admitted by the supply pipe $5 will be cooled more rapidly and willtake up a large amount of moisture. In

order to insure that the increments of the stream T flowing in themedian region of the condensing chamber 2a are not subjected to theaction of an overlying moist current of air, the operator will shift theevacuating device 76 (i.e., the hood 6 in a direction toward the supplypipe 36 so that the first current of air is evacuated after a relativelyshort-lasting contact with the tobacco particles. The effect of therelatively dry second air current which issues from the second supplypipe 56 is then felt along a greater portion of the drier 2. By the sametoken, the operator might wish to adjust the evacuating device 76 in theopposite direction to thereby prevent long-lasting contact of tobaccowith a relatively moist current of air which is adiitted by the pipe 56.

Under certain circumstances, the operators might wish to condition agiven brand of tobacco particles by heat which is supplied by only oneor two heating units. This can be achieved by hutting off the auxiliaryheating unit 148, by partially shutting of the unit 148, or by shuttingd the unit 143 (either partially or completely) and by simultaneouslyshutting off or by at least reducing the conditioning action of one ofthe adjustable heating units 23, 48. Such operation will be warrantedwhen the moisture content of the tobacco stream is only slightly higherthan the desired moisture content. Also, the auxiliary heating unit 148can be omitted altogether, especially if the adjustable heating units28, 48 are capable of supplying the basic amount of heat energy plussuch heat energy which fluctuates in response to impulses transmitted bythe various detectors of the two control units. The wall 62 is thenheated solely by air currents which are discharged by such adjustableheating units.

The improved conditioning apparatus is susceptible of many additionalmodifications without departing from the spirit of my invention. Forexample, the components 66, 68 of the evacuating device 76 can bemounted in such a way that they can rotate with or with reference to thehood 64 about the axis of the drier 2. This can be achieved by changingthe angular position of the spindle nut 72 with reference to the drier 2so that the hose 112 can be moved to a plurality of angular positionsincluding the one occupied by the hose 112' shown in FIG. 2. Suchangular displacement of the hose 112 can be carried out withoutnecessitating rotation of the fan 68a which is connected to the pipe 68,i.e., the hose 112 can be long enough to allow for rotation of thefunnel 66 and pipe 68 through up to 180 degrees in either direction.

The construction of the apparatus shown in FIGS. 1 to 3 can besimplified if the hood 64 remains in a selected axial position so thatthe spindle 7i nut '72 and hand wheel 74 can be dispensed with. Thecollars 8t 82 are then placed into abutment with the flanges 65, 67.These collars are preferably adjustable in the axial direction of thedrier 2. In such modified construction, the hood 64 can be held againstrotation with the cylindrical wall 62 by means of a suitable arrestingdevice, for example, a brake shoe or the like.

It is also possible to provide a common source of hot fluid for theadjustable heating units 28 and 48, i.e., the supply pipes 36, 56 canreceive hot air from a common lower. The valves 38, 50 are theninstalled directlly in the supply pipes 36, 56 and are adjustable by theservomotors 4t), 52 to respectively regulate the admission of hot air independency on changes in the characteristics of the tobacco stream Tupstream and downstream of the drier 2. Instead of resortin to a commonsource of hot fluid for the supply pipes 36, 56, at least one of thesepipes can receive hot air from two or more blowers. Also, at least oneof the heating units 28, 48 can comprise two or more supply pipes, atleast one blower for each such supply pipe, and a separate valve forregulating the temperature of hot air passing through each supply pipe.For example, and if the heating unit 28 were to be replaced by a heatingunit having two blowers 28, two supply pipes 36, two suction pipes 32,two nipples 37 and two heaters 30, the control unit 135 would beprovided with two valves 38 one of which would regulate the temperatureof hot air in one of the supply pipes as a function of measurementscarried out by the weighing device 12a and the other of which wouldregulate the temperature of hot air in the other supply pipe as afunction of measurements carried out by the dielectric moisture detectorincluding the trough 14.

Furthermore, the axial ends of the wall 62 can remain open if the pipe68 is connected with the fan 68a or with another suitable suctiongenerating device. The suction in the funnel as and compartment 113should be strong enough to prevent escape of hot air at the axial endsof the drier 2. However, and assuming that the axial ends of the drier 2are open, suction in the compartment 113 should not be overly strongbecause, otherwise, the fan or fans connected with the pipe 68 woulddraw cold atmospheric air at the upstream and downstream ends of theconditioning chamber 2a. In order to avoid such uncontrolled admissionof cool atmospheric air, the axial ends of the drier 2 are preferablysealed in a manner as pointed out hereinabove. For example, theright-hand axial end of the drier can be sealed by the header 24a whichprovides just enough room for escape of conditioned tobacco into thechute 18. Each of the chutes 1-6, 18 may include a conventional air lockone of which permits entry of tobacco particles but prevents entry ofair and the other of which permits escape of tobacco particles but holdsback air. If such air locks are used, the blowers 34, 134 and the fan68a willl be preferably adjusted in such a way that the conditioningchamber 2a is maintained at a pressure which is slightly higher thanatmospheric pressure. This will insure that the air locks will not admitcold air if the rate at which the tobacco stream T is being fed isreduced below an average value, i.e., when the rate of tobacco feeddecreases, the air locks will permit escape of hot air from the chamber2a but will not permit entry of cool atmospheric air.

Finally, it is equally possible to construct the hood 64 in such a waythat it defines with the wall 62 two or more separate compartments 113each of which can be connected with the pipe 68 independently of theother compartment or compartments. In this way, the operators cancontrol the rate at which the evacuating device withdraws hot air andvapors from the chamber 2a.

The method of my invention can be shortly described as comprising thebasic steps of conveying a continuous stream T of moist tobaccolengthwise along a predetermined path defined by the feed 10, 12, 16. 8,18, 20 toward and beyond an elongated conditioning zone (chamber 211)which includes a first section (between the chute 16 and the centralportion of the hood 64) which is first to receive successive incrementsof tobacco and a second section (between the central portion of the hood64 and the chute 18) which receives successive increments from the firstsection, admitting into the first section of the conditioning zone afirst current of hot fluid (supply pipe 36) and conveying such hot fluidconcurrent with the stream T so that the fluid expels moisture fromtobacco, admitting into the second section of the conditioning zone asecond current of hot fluid (supply pipe 56) and conveying the secondcurrent countercurrent to the stream T so that the second current expelsadditional moisture from tobacco, and evacuating the two currents fromthe conditioning zone in the region (compartment 113) between the twosections. By moving the region of evacuation lengthwise of theconditioning zone, the operators can lengthen one of the aforementionedsections at the expense of the other section, or vice versa.

Without further analysis, the foregoining will so fully reveal the gistof the present invention that others can, by applying current knowledge,readily adapt it for various applications without omitting featureswhich fairly constitute essential characteristics of the generic andspecific aspects of my contribution to the art and, therefore, suchadaptations should and are intended to be 13 comprehended within themeaning and range of equivalence of the following claims.

What is claimed as new and desired to be protected by Letters Patent is:

1. A tobacco conditioning apparatus, comprising a feed arranged toadvance a stream of moist tobacco lengthwise toward, through and beyonda conditioning zone; a drier accommodated in said zone and defining acontinuous conditioning chamber having an intake end which receivessuccessive increments of the stream and a discharge end from which suchincrements issue; heaitng means comprising first supply means foradmitting into said intake end at least one first current of hot fluidwhich flows concurrent with the stream and expels moisture from tobacco,and second supply means for admitting into said discharge end at leastone second current of hot fluid which flows countercurrent to the streamand expels additional moisture from tobacco; and evacuating meanscommunicating with said conditioning chamber intermediate said intakeand discharge ends for receiving the currents from said drier andexhausting them from the chamber.

2. An apparatus as set forth in claim 1, wherein said heating meansfurther comprises blower means for delivering hot air to said supplymeans.

3. An apparatus as set forth in claim 1, wherein said heating meanscomprises two heating units each including one of said supply means andat least one hot air blower for delivering hot air to the respectivesupply means.

4. An apparatus as set forth in claim 1, wherein said heating meansfurther comprises an adjustable heating unit including one of saidsupply means, and further comprising control means for said heatingunit, said control means comprising detector means for measuring themoisture content of succesive incremnets of the stream outside of saidconditioning chamber and adjusting means for regulating the temperatureof heating fluid which is admitted into said chamber by said one supplymeans in accordance with the results of measurements carried out by saiddetector means.

5. An apparatus as set forth in claim 4, wherein said one supply meansis said first supply means and wherein said detector means is arrangedto measure the moisture content of successive increments prior to entryof such increments into said conditioning chamber.

6. An apparatus as set forth in claim 5, wherein said control meansfurther comprises servomotor means for operating said adjusting meansonly when the results of measurements carried out by said detector meansdeviate from a predetermined value.

7. An apparatus as set forth in claim 5, wherein said control meansfurther comprises second detector means for measuring the weight ofsuccessive incremnets on their way to said intake end and wherein saidadjusting means is arranged to regulate the temperature of hot fluidadmitted by said first supply means in accordance with the results ofmeasurements carried out by said second detector means so that thetemperature of fluid in said first current is higher if the stream isfed at a higher rate and that the temperature of fluid is lower if thestream is fed at a reduced rate.

8. An apparatus as set forth in claim 7, wherein said control meansfurther comprises servomotor means for operating said adjusting meansonly when the combined results of measurements carried out by both saiddetector means deviate from a predetermined value.

9. An apparatus as set forth in claim 4, wherein said one supply meansis said second supply means and wherein said detector means is arrangedto determine the moisture content of successive increments after suchin- .crements issue from said conditioning chamber.

10. An apparatus as set forth in claim 9, wherein said control meansfurther comprises servomotor means for operating said adjusting meansonly when the results of i i measurements carried out by said detectormeans deviate from a predetermined value.

11. An apparatus as set forth in claim 9, wherein said control meansfurther comprises damper means for preventing sudden changes in thetemperature of hot fluid admitted by said second supply means.

12. An apparatus as set forth in claim 1, wherein said heating meanscomprises first and second adjustable heating units which respectivelyinclude said first and second supply means, and further comprising firstcontrol means including first detector means for measuring the moisturecontent of tobacco prior to entry of such tobacco into said chamber andadjusting means for regulating the temperature of hot fluid admitted bysaid first supply means in accordance with the results of suchmeasurements, and second control means including second detector meansfor measuring the moisture content of tobacco downstream of said chamberand adjusting means for regulating the temperature of hot fluid admittedby said second supply means in accordance with the results ofmeasurements carried out by said second detector means.

13. An apparatus as set forth in claim 12, wherein each of said detectormeans is arranged to determine the moisture content of tobacco insuccessive increments of said stream.

14. An apparatus as set forth in claim 1, wherein said conditioningchamber is elongated and wherein said evacuating means comprises amember movable in the longitudinal direction of said chamber to increasethe moisture expelling effect of one of said currents at the expense ofthe other current, or vice versa.

15. An apparatus as set forth in claim 1, wherein said drier comprises atubular wall surrounding said conditioning chamber and having a medianportion provided with perforations through which said evacuating meanscan communicate With said chamber.

16. An apparatus as set forth in claim 15, wherein said tubular wall isrotatable about its own axis and wherein said evacuating means comprisesa hood sur-; rounding said wall and defining with said median portion atleast one compartment which communicates with said chamber through atleast some of said perforations.

17. An apparatus :as set forth in claim 16, further comprising means forholding said hood against rotation with said wall.

18. An apparatus as set forth in claim 16, wherein said compartmentextends circumferentially around the entire median portion of said wall.

19. An apparatus as set forth in claim 16, where-in the length of saidcompartment is less than the length of said median portion, as seen inthe axial direction of said wall.

20. An apparatus as set forth in claim 19, further comprising means formoving said hood axially of said wall.

21. An apparatus as set forth in claim 20, wherein said evacuating meansfurther comprises :a substantially funnel-shaped portion whosecross-sectional area diminishes in a direction away from saidcompartment, said funnel-shaped portion being connected with said hoodand communicating with said compartment.-

22. An apparatus as set forth in claim 16, further comprising means formoving said hood axially of said wall and stop means for limiting suchmovements of said hood.

23. An apparatus as set forth in claim 22, wherein said hood comprisesportions which seal at least some of said perforations, at least whensaid hood abuts against said stop means.

24. An apparatus :as set forth in claim 22, wherein the means for movingsaid hood comprises manually operable actuating means.

25. An apparatus as set forth in claim 1, wherein said heating meanscomprises :an auxiliary heating unit provided in said chamber andarranged to expel moisture 15 from tobacco in addition to such moisturewhich is expelled by said currents of hot fiuid.

26. An apparatus as set forth in claim 25, wherein said drier comprisesa rotary cylindrical wall which surrounds said conditioning chamber andsaid auxiliary heating unit comprises heating elements extendingsubstantially all the way between said intake and discharge ends andbeing supported by and rotatable with said wall so that such heatingelements transmit heat energy to said wall and simultaneously agitatethe tobacco in said chamber.

27. An apparatus as set forth in claim 1, wherein said evacuating meanscomprises suction generating means for drawing said currents from saidconditioning chamber.

28. An apparatus as set forth in claim 1, wherein said hot fluid is airand further comprising control means for regulating the temperature ofhot air admitted by said first and second supply means as a function ofthe moisture content of tobacco in successive increments of the streamrespectively measured prior to and subsequent to passage of suchincrements through said conditioning chamber, said control means furthercomprising means for comparing the measured moisture content with apredetermined value and means for adjusting the temperature of hot airin the respective supply means when the result of measurement upstreamor downstream of said chamber deviates from the respective predeterminedvalue.

29. A method of conditioning tobacco, comprising the steps of conveyinga continuous stream of moist tobacco lengthwise along a predeterminedpath toward, through and beyond an elongated continuous conditioningzone having a first section which is first to receive successiveincrements of tobacco and a second section which receives successiveincrements from said first section; admitting into said first section afirst current of hot fluid and conveying such fluid concurrent with thestream so that the fluid expels moisture from tobacco; admitting intosaid second section a second current of hot fluid and conveying thesecond current counter-current to the 16 stream toward said firstsection so that the second current expels additional moisture fromtobacco; and evacuating and expelling said currents from saidconditioning zone in the region between said sections.

30. A method as set forth in claim 29, further comprising the step ofmoving said region lengthwise of said conditioning zone to lengthen oneof said sections at the expense of the other section, or vice versa.

31. A method as set forth in claim 29, further comprising the steps ofmeasuring the moisture content of tobacco in successive increments ofthe stream upstream and downstream of said conditioning zone, regulatingthe temperature of said first current in accordance with the results ofmeasurements upstream of said zone, and regulating the temperature ofsaid second current in accordance with the results of measurementsdownstream of said zone.

References Cited UNITED STATES PATENTS 1,393,086 10/1921 Carrier 131-1351,551,676 9/1925 McConnell 131-136 X 1,823,554 9/1931 Mewborne 131-133 X1,976,487 10/1934 El'berty 68-9 2,322,272 6/1943 Bailey et al 34-46 X2,596,183 5/1952 Sowa 131-140 2,679,115 5/1954 Bogaty et al 131-136 X2,768,629 10/1956 Maul 131-135 2,882,910 4/1959 Jones et al. 131-1352,933,090 4/1960 Hamilton et al 131-140 3,102,794 9/1963 Arnold 34-46 XFOREIGN PATENTS 1,416,676 9/1965 France.

1,499 4/ 1881 Great Britain. 953,893 4/1964 Great Britain.

ALDRICH F. MEDBERY, Primary Examiner.

29. A METHOD OF CONDITIONING TOBACCO, COMPRISING THE STEPS OF CONVEYING A CONTINUOUS STREAM OF MOIST TOBACCO LENGTHWISE ALONG A PREDETERMINED PATH TOWARD, THROUGH AND BEYOND AN ELONGATED CONTINUOUS CONDITIONING ZONE HAVING A FIRST SECTIN WHICH IS FIRST TO RECEIVE SUCCESSIVE INCREMENTS OF TOBACCO AND A SECOND SECTION WHICH RECEIVES SUCCESSIVE INCREMENTS FROM SAID FIRST SECTION; ADMITTING INTO SAID FIRST SECTION A FIRST CURRENT OF HOT FLUID AND CONVEYING SUCH FLUID CONCURRENT WITH THE STREAM SO THAT THE FLUID EXPELS MOISTURE FROM TOBACCO; ADMITTING INTO SAID SECOND SECTION A SECOND CURRENT OF HOT FLUID AND STREAM TOWARD SAID FIRST SECTION SO THAT THE SECOND CURRENT EXPELS ADDITIONAL MOISTURE FROM TOBACCO; AND EVACUATING 